"stretched tight," 1660s, from Latin tensus, past participle of tendere "to stretch, extend," from PIE root *ten- "to stretch." Figurative sense of "in a state of nervous tension" is first recorded 1821. Related: Tensely; tenseness.
"form of a verb showing time of an action or state," early 14c., tens "time," also "tense of a verb" (late 14c.), from Old French tens "time, period of time, era; occasion, opportunity; weather" (11c., Modern French temps), from Latin tempus "a portion of time" (also source of Spanish tiempo, Italian tempo; see temporal).
"to make tense," 1670s, from tense (adj.); intransitive sense of "to become tense" (often tense up) is recorded from 1946. Related: Tensed; tensing.